Managing for Salmon Resilience in California’s Variable and Changing Climate

Bruce Herbold,Rene Henery,Stephanie M Carlson

doi:10.15447/sfews.2018v16iss2art3

Abstract

Author(s): Herbold, Bruce; Carlson, Stephanie M.; Henery, Rene; Johnson, Rachel C.; Mantua, Nate; McClure, Michelle; Moyle, Peter B.; Sommer, Ted | Abstract: California’s salmonids are at the southern limits of their individual species’ ranges, and display a wide diversity of strategies to survive in California’s highly variable climate. Land use changes after statehood in 1850 eliminated important habitats, or blocked access to them, and reduced the abundance, productivity, and distribution of California’s salmon. Habitat simplification, fishing, hatchery impacts, and other stressors led to the loss of genetic and phenotypic (life history, morphological, behavioral, and physiological) diversity in salmonids. Limited diversity and habitat loss left California salmon with reduced capacity to cope with a variable and changing climate. Since 1976, California has experienced frequent droughts, as were common in the paleo-climatological record, but rare in the peak dam-building era of 1936–1976. Increasing temperatures and decreasing snowpacks have produced harsher conditions for California’s salmon in their current habitats than they experienced historically. The most likely way to promote salmon productivity and persistence in California is to restore habitat diversity, reconnect migratory corridors to spawning and rearing habitats, and refocus management to replenish the genetic and phenotypic diversity of these southernmost populations.

Highlights

Salmon in California had access to diverse freshwater and estuarine habitats, and display an array of life history and physiological adaptations to the challenges posed by the dynamic climate
Diverse habitats for diverse genotypes and phenotypes can provide a portfolio of options to support sustainable salmon populations in challenging climates (Hilborn et al 2003; Figge 2004; Koellner and Schmitz 2006; Schindler et al 2010, 2015)
Diverse phenotypes allowed adaptation to local conditions and produced populations resilient to fire, flood, earthquake, landslide, and drought. This diversity is exemplified by the Central Valley Chinook Salmon complex, comprising four distinct runs named for their respective seasons of adult migration (Fry 1961) (Figure 3)

Summary

INTRODUCTION

Large coastal basins like the Klamath/Trinity have substantial catchment areas at both high and low elevations This produces a “transitional” hydrograph with high runoff from fall and winter rains, and snowmelt runoff in spring to early summer. Variability in annual precipitation (Figure 2) is higher in California than in any other state in the continental US (Dettinger 2011) This variability rests entirely on November–May precipitation, producing extreme fluctuations in freshwater salmon habitat quality and quantity. Diverse phenotypes allowed adaptation to local conditions and produced populations resilient to fire, flood, earthquake, landslide, and drought This diversity is exemplified by the Central Valley Chinook Salmon complex, comprising four distinct runs named for their respective seasons of adult migration (Fry 1961) (Figure 3).

Million hectares

Findings

CONCLUSIONS